1. Field of the Invention
The present invention relates generally to agricultural implements and, more particularly, to a depth control system which is mountable to an implement for controlling the height of the implement, and which incorporates a cab mounted monitor for controlling a desired depth for the implement.
2. Related Prior Art
Various control mechanisms have been proposed for controlling the depth setting for implements such as field cultivators and other implements for which there is a need to maintain a predetermined soil penetration depth. Many of the improvements have been directed to providing control of the three point hitch on a tractor supporting the implement. For example, electronic control systems including electronic microprocessors have been combined with the hydromechanical systems of tractors in order to provide more precise control of the valving controlling the position of the links for the three point hitch.
Examples of prior art electronic position control systems for controlling the position of a linkage supporting an implement on a tractor include U.S. Pat. Nos. 4,343,365 to Rajagopal et al., 4,132,272 to Holloway et al. and 5,012,415 to Boe et al. While tractors provided with the devices disclosed in these patents provide improved position control for the implements supported on the tractor, the position sensing is provided at the tractor rather than at the implement adjacent to the soil engaging tool, such that the position sensing operation is performed at a location distanced from the actual work area of the tool. In such a control system, it is difficult to provide accurate feedback as to the precise position or depth penetration of the tools. Further, such systems are typically factory installed and do not address the problem of providing a depth control system for use with implements engaged on tractors which do not have such depth control systems.
U.S. Pat. No. 4,355,688 to Hamm et al. discloses an agricultural implement and associated depth control system wherein the depth control system is mounted to the implement and actuates a cylinder for positioning the height of the implement relative to the soil, depending on varying soil conditions to maintain a preselected tillage depth. This control system requires that the selected tillage depth be adjusted at the implement, and does not include a control for permitting an operator to selectively adjust the depth from the cab of the tractor. In addition, this depth control device provides a control which varies the depth positioning of the implement depending on varying responses from a vertically pivoting wheel which is in contact with the tilled ground, and accordingly would not be functional to provide exact control of a fixed working depth such as is required during a tillage operation by a field cultivator.
Accordingly, there is a need for a control system for providing accurate depth control of an implement wherein the depth control system may be operated from the cab of a tractor, and wherein the control system may be used with a wide range of tractors and implements.